Couldn't add multiple iframes in my CMS page from admin panel

I need to add multiple iframes in my music page. I want it to be done from admin panel. I added these lines clicking edit HTML source of the editor but greater than and less than sign are replaced by &lt;/p&gt; &lt;p&gt;&lt;. I am newbie to silverstripe. Any help will be appreciated.

I had done some research and tried adding these lines in mysite/_config.php
HtmlEditorConfig::get('cms')->setOption('verify_html', 'false');
HtmlEditorConfig::get('cms')->setOption('element_format', 'html');
HtmlEditorConfig::get('cms')->setOption('cleanup', 'false');